Conventionally, a technique for producing ethanol or the like, in which solid-liquid separation is performed after saccharification of biomass such as wood by using diluted sulfuric acid or concentrated sulfuric acid, and a liquid phase is neutralized and used as a raw material for ethanol fermentation, has been practically utilized (Patent Literature 1, Patent Literature 2).
Further, production of chemical industrial raw materials (for example, lactic acid fermentation) using saccharide as a starting material can also be considered.
In this specification, “biomass” represents organisms incorporated in a substance circulatory system of the global biosphere or accumulation of organic matters derived from the organisms (see JIS K 3600 1258).
Sugarcane, corn and the like, which are currently used as alcohol raw materials, are originally used as food and using these edible resources as industrial resources in a long term and in a stable manner is not preferable in view of a life cycle of effective foodstuff.
Therefore, it is an important issue to effectively use cellulose resources such as herbaceous biomass and woody biomass, which are believed to be useful industrial recourses in the future.
Further, in the cellulose resources, the resource component ratio is varied such that the ratio of cellulose is 38% to 50%, that of hemicellulose component is 23% to 32%, and that of lignin component, which is not used as a fermentation raw material, is 15% to 22%. Because industrial researches have been conducted with many unsolved problems, raw materials in the researches are assumed in a fixed manner, and currently there is no disclosure of a technique of a production system with taking the material versatility into consideration.
Originally, because issues of waste and prevention of the global warming are taken into consideration according to a method unfavorable to fermentation feedstock as compared with starch feedstock, there is less point in the production system in which raw materials are considered in a fixed manner. This production system should be widely applicable to general waste materials. Enzymatic saccharification method itself is not efficient at all, and is thought to be a challenge of the future. A saccharification rate by acid treatment has a considerably small value of about 75% (on a component basis capable of being saccharified) due to excessive decomposition of saccharide caused by overreaction. Therefore, the production yield of ethanol is about 25% with respect to the cellulose resources (Non Patent Literature 1, Patent Literature 3).
In the conventional techniques disclosed in Patent Literatures 1 to 3, there has been a phenomenon in which a reaction by-product causes inhibition of enzymatic saccharification to decrease the saccharide yield. Therefore, a hydrothermal decomposition apparatus that removes a substance inhibiting enzymatic saccharification to increase activity of enzyme based on cellulose has been proposed (Patent Literatures 4 and 5).